全文获取类型
收费全文 | 18512篇 |
免费 | 1722篇 |
国内免费 | 765篇 |
专业分类
电工技术 | 1186篇 |
技术理论 | 1篇 |
综合类 | 1165篇 |
化学工业 | 2999篇 |
金属工艺 | 1004篇 |
机械仪表 | 1194篇 |
建筑科学 | 1688篇 |
矿业工程 | 604篇 |
能源动力 | 552篇 |
轻工业 | 1077篇 |
水利工程 | 350篇 |
石油天然气 | 1162篇 |
武器工业 | 116篇 |
无线电 | 2231篇 |
一般工业技术 | 2323篇 |
冶金工业 | 850篇 |
原子能技术 | 197篇 |
自动化技术 | 2300篇 |
出版年
2024年 | 91篇 |
2023年 | 330篇 |
2022年 | 594篇 |
2021年 | 890篇 |
2020年 | 653篇 |
2019年 | 475篇 |
2018年 | 581篇 |
2017年 | 633篇 |
2016年 | 556篇 |
2015年 | 784篇 |
2014年 | 927篇 |
2013年 | 1165篇 |
2012年 | 1190篇 |
2011年 | 1224篇 |
2010年 | 1103篇 |
2009年 | 1015篇 |
2008年 | 1024篇 |
2007年 | 929篇 |
2006年 | 959篇 |
2005年 | 876篇 |
2004年 | 563篇 |
2003年 | 499篇 |
2002年 | 524篇 |
2001年 | 425篇 |
2000年 | 453篇 |
1999年 | 478篇 |
1998年 | 375篇 |
1997年 | 326篇 |
1996年 | 294篇 |
1995年 | 256篇 |
1994年 | 205篇 |
1993年 | 129篇 |
1992年 | 108篇 |
1991年 | 108篇 |
1990年 | 72篇 |
1989年 | 56篇 |
1988年 | 35篇 |
1987年 | 28篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
Sun Linzhi Luo Yi Zhang Yanan Sun Ping Qin Xinjie Gong ZhenbangPrecision Machinery Institute Shanghai University Shanghai China 《机械工程学报(英文版)》2002,15(4):303-307
An experimental bimorph piezoelectric element (PZT) actuator for small pipe robot is developed. The robot can move in φ20 mm pipe, and can carry a CCD camera for detecting cracks or fine holes on inner surface of pipe. The velocity of the robot can reach 17~22 mm/s for vertical pipe up/down, respectively. Moving principle and its performance characteristics are presented. 相似文献
82.
This paper presents a novel approach to computing tight upper bounds on the processor utilization for general real-time systems where tasks are composed of subtasks and precedence constraints may exist among subtasks of the same task. By careful analysis of preemption effects among tasks, the problem is formulated as a set of linear programming (LP) problems. Observations are made to reduce the number of LP problem instances required to be solved, which greatly improves the computation time of the utilization bounds. Furthermore, additional constraints are allowed to be included under certain circumstances to improve the quality of the bounds. 相似文献
83.
对原有的冶金矿山设计和生产不同能耗指标,提出统一为一个指标体系的设想,并提出了指标体系的计算公式以及各系数的选取意见。 相似文献
84.
85.
瀑布沟水电站导流洞渐变段临时中墩的拆除,采用了微差起爆网络的控制爆破技术,取得了很好的效果。本文着重介绍控制爆破的施工方法、设计依据、设计参数以及爆破方式等。 相似文献
86.
A. Nakayama A. Kakugo J.P. Gong Y. Osada M. Takai T. Erata S. Kawano 《Advanced functional materials》2004,14(11):1124-1128
Double‐network (DN) hydrogels with high mechanical strength have been synthesized using the natural polymers bacterial cellulose (BC) and gelatin. As‐prepared BC contains 90 % water that can easily be squeezed out, with no more recovery in its swelling property. Gelatin gel is brittle and is easily broken into fragments under a modest compression. In contrast, the fracture strength and elastic modulus of a BC–gelatin DN gel under compressive stress are on the order of megapascals, which are several orders of magnitude higher than those of gelatin gel, and almost equivalent to those of articular cartilage. A similar enhancement in the mechanical strength was also observed for the combination of BC with polysaccharides, such as sodium alginate, gellan gum, and ι‐carrageenan. 相似文献
87.
88.
In order to enhance the readability and to simplify the verification of temporal logic programs in the XYZ system,we propose a structured temporal logic language called XYZ/SE,based on XYZ/BE which is the basis language of the XYZ system.A set of proof rules are given and proved to be sound and adequate for proving the partial correctness of XYZ/SE programs in a compositional way.Moreover,we show that every XYZ/BE program can be transformed into an equivalent XYZ/SE program.So we have developed a general conpositional verification method in the XYZ system concerning the sequential case. 相似文献
89.
Synthesis and properties of polystyrene/graphite nanocomposites 总被引:3,自引:0,他引:3
In this paper, graphite/polystyrene nanocomposite is synthesized by in situ polymerization of styrene in a tetrahydrofuran (THF) solution system of potassium (K)-THF-graphite intercalation compound (GIC). K-THF-GIC has proved to initiate polymerization of styrene by the anionic mechanism. Due to the interfacial interaction between the graphite nanolayers and the polymer, the composites exhibit higher glass transition temperature and higher thermal stability when compared to polystyrene. The percolation threshold in the conductivity of the composites is lesser than 8.2 wt% and the dielectric constant can reach as high as 136. 相似文献
90.
The problem of radio wave propagation over a perfectly conducting, infinitely wide rectangular plateau of finite length has previously been solved. (see Electron. Lett., vol.25, p.707-9, 1989). This solution is now extended to deal with a perfectly conducting, rectangular plateau of finite size along all three coordinate axes. When the infinite width is reduced to a finite size the additional diffraction round the two sides of the plateau will produce a more complicated expression for the overall attenuation. The authors quantify the new attenuation and derive an approximate analytic expression for the attenuation function in closed form. Experimental confirmation of the calculated result both as a function of distance along the propagation path and as a function of transverse displacement of the plateau perpendicular to the propagation path is presented 相似文献